Sahl ibn Abu Hathmah came to our gathering. He said: The Messenger of Allah ﷺ commanding us said: When you estimate take them leaving a third, and if you do not leave or find a third, leave a quarter. (Using translation from Abū Dāʾūd 1605)
أَمَرَنَا رَسُولُ اللهِ ﷺ قَالَ إِذَا خَرَصْتُمْ فَخُذُوا وَدَعُوا الثُّلُثَ فَإِنْ لَمْ تَدَعُوا الثُّلُثَ فَدَعُوا الرُّبُعَ